Six halo-acidophilic archaeal strains were isolated from four commercial salt samples obtained from seawater in the Philippines, Indonesia (Bali) and Japan (Okinawa) on agar plates at pH 4.5. Cells of the six strains were pleomorphic, and stained Gram-negative. Two strains were pink–red pigmented, while four other strains were orange–pink pigmented. Strain MH1-16-3T was able to grow at 9–30 % (w/v) NaCl [with optimum at 18 % (w/v) NaCl], at pH 4.5–6.8 (optimum, pH 5.5) and at 20–50 °C (optimum, 42 °C). The five other strains grew at slightly different ranges. The six strains required at least 1 mM Mg2+ for growth. The 16S rRNA gene sequences of the six strains were almost identical, sharing 99.9 (1–2 nt differences) to 100 % similarity. The closest relatives were Halarchaeum acidiphilum MH1-52-1T and Halarchaeum salinum MH1-34-1T with 97.7 % similarity. The DNA G+C contents of the six strains were 63.2–63.7 mol%. Levels of DNA–DNA relatedness amongst the six strains were 79–86 %, while those between MH1-16-3T and H. acidiphilum MH1-52-1T and H. salinum MH1-34-1T were both 43 and 45 % (reciprocally), respectively. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the six isolates represent a novel species of the genus Halarchaeum , for which the name Halarchaeum rubridurum sp. nov. is proposed. The type strain is MH1-16-3T ( = JCM 16108T = CECT 7535T).
Strain CC65T, a novel extremely halophilic archaeon, was isolated from a brine sample of a salt lake in Iran. The novel strain was light yellow-pigmented, non-motile, pleomorphic and required at least 1.7 M NaCl and 0.02 M MgCl2 for growth. Optimal growth was achieved at 3.5 M NaCl and 0.4 M MgCl2. The optimum pH and temperature for growth were pH 7.5 and 40 °C, respectively, while it was able to grow over a pH and a temperature range of pH 6.5–9.0 and 30–50 °C, respectively. Analysis of 16S rRNA gene sequence revealed that strain CC65T clustered with the sole member of the genus Halopenitus , Halopenitus persicus DC30T with a sequence similarity of 98.0 %. The polar lipid profile of strain CC65T consisted of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. An unidentified glycolipid and two minor phospholipids were also observed. The only quinone present was MK-8(II-H2). The DNA G+C content of strain CC65T was 63.8 mol%. On the basis of the biochemical and physiological characteristics, as well as DNA–DNA hybridization (44 % with Halopenitus persicus IBRC 10041T), strain CC65T is classified as a novel species of the genus Halopenitus , for which the name Halopenitus malekzadehii sp. nov. is proposed. The type strain is CC65T ( = IBRC-M 10418T = KCTC 4045T).